The excitation and breaking of relativistically intense electron-ion modes in a cold plasma is studied using 1D-fluid simulation techniques. To excite the mode, we have used a relativistic rigid homogeneous electron beam propagating inside a plasma with a velocity close to the speed of light. It is observed that the wake wave excited by the electron beam is identical to the corresponding Khachatryan mode, a relativistic electron-ion mode in a cold plasma. It is also seen in the simulation that the numerical profile of the excited electron-ion mode gradually modifies with time and eventually breaks after several plasma periods exhibiting explosive behavior in the density profile. This is an well known phenomena, known as wave breaking. It is found that the numerical wave breaking limit of these modes lies much below than their analytical breaking limit. The discrepancy between the numerical and analytical wave breaking limit has been understood in terms of phase-mixing process of the mode. The phase mixing time (or wave breaking time) obtained from the simulations has also been scaled as a function of beam parameters and found to follow the analytical scaling.
The spatio-temporal evolution and breaking of relativistically intense wave packets in a cold homogeneous unmagnetized plasma has been studied analytically and numerically. A general expression for phase mixing time scale as a function of amplitude of the wave packet and width of the spectrum has been derived. Results have been compared with the existing formulae in literature. It is shown that phase mixing time scale crucially depends on the relative magnitude of the amplitude and dimensionless spectral width of the wave packet. Finally we have verified our results with respect to both the am…
Space-time evolution of relativistic electron beam driven wake-field in a cold, homogeneous plasma, is studied using 1D-fluid simulation techniques. It is observed that the wake wave gradu- ally evolves and eventually breaks, exhibiting sharp spikes in the density profile and sawtooth like features in the electric field profile [1]. It is shown here that the excited wakefield is a longitudi- nal Akhiezer-Polovin mode [2] and its steepening (breaking) can be understood in terms of phase mixing of this mode, which arises because of relativistic mass variation effects. Further the phase mixing ti…
Fluid simulations, which are considerably simpler and faster, have been employed to study the behavior of the wakefield driven by a relativistic rigid beam in a 2-D cold plasma. When the transverse dimensions of the beam are chosen to be much larger than its longitudinal extent, a good agreement with our previous 1-D results [\textcolor{red}{\it Physics of Plasmas 22, 073109 (2015)}] are observed for both under-dense and over-dense beams. When the beam is overdense and its transverse extent is smaller or close to the longitudinal extension, the 2-D blow-out structure, observed in PIC simulatio…
Breaking seed dormancy in Mediterranean Brassica rapa wild populations: is cold plasma treatment efficient?
GEVES, Station Nationale d'Essais de Semences（GEVES国家种子试验站）；Sorbonne Université（索邦大学）；University of Palermo（巴勒莫大学）；University of Sciences and Technology Houari Boumediene USTHB（胡阿里·布迈丁科学技术大学）；IGEPP Institut de Génétique Environnement et Protection des Plantes Bretagne-Normandie（布列塔尼-诺曼底植物遗传环境及保护研究所）
Spatio-temporal evolution of a non-relativistic electrostatic waves in a cold plasma has been studied in the wave-breaking regime using a 1D particle-in-cell simulation. It is found that plasma gets heated after the wave-breaking but a fraction of initial energy always remains with the remnant wave in the form of BGK mode in warm plasma. An interesting finding of this work is that the frequency of the resultant BGK wave is found be below electron plasma frequency which decreases with increasing initial amplitude. Moreover, the acceleration mechanism after the wave-breaking is also found to be …
The Cauchy problem for a quasilinear system of hyperbolic equations describing plane one-dimensional relativistic oscillations of electrons in a cold plasma is considered. For some simplified formulation of the problem, a criterion for the existence of a global in time solutions is obtained. For the original problem, a sufficient condition for the loss of smoothness is found, as well as a sufficient condition for the solution to remain smooth at least for time $ 2 π$. In addition, it is shown that in the general case, arbitrarily small perturbations of the trivial state lead to the formation o…
We discuss some general and relevant features of longitudinal gravitational modes in Horndeski gravity and their interaction with matter media. Adopting a gauge-invariant formulation we clarify how massive scalar and vector fields can induce additional transverse and longitudinal excitations, resulting in breathing, vector and longitudinal polarizations. We review, then, the interaction of standard gravitational waves with a molecular medium, outlining the emergence of effective massive gravitons, induced by the net quadrupole moment due to the molecule deformation. Finally, we investigate the…
Adapting a plane hydrodynamical model we briefly revisit the study of the impact of a very short and intense laser pulse onto a diluted plasma, the formation of a plasma wave, its wave-breaking, the occurrence of the slingshot effect.
For a system of equations describing one-dimensional nonlinear oscillations in a magnetoactive plasma, we study the effect of a constant magnetic field on the breaking of oscillations. For the nonrelativistic case, a criterion for the formation of a finite-dimensional singularity is obtained in terms of the initial data. It is shown that the enhancement of the magnetic field basically leads to an expansion of the class of initial data providing the global smoothness of the solution. The nature of the singularities of the solutions is illustrated by numerical examples.
